A mass call event (MCE) is a situation in which an extraordinary high number of phone calls are simultaneously attempted in a telephone communication system. Typically, an MCE is triggered by a sudden emergency, such as the 2001 September 11 terrorist attack and the 2013 Boston Marathon bombing. During an MCE, mass notification systems (MNSs) may, as part of a notification scheme, cause the generation a large number of telephone calls, typically using one or more automated telephone dialing systems. The large number of calls during an MCE can congest or flood the telephone system, degrade telephony services, and even make the services completely unavailable.
Like reference numbers and designations in the various drawings indicate like elements.